Method of die-forming parts with improved grain structure

ABSTRACT

A method of die-forming parts so that, in their final shape, they have a substantially continuous grain structure, whereby a cylindrical blank is shaped into a spherical part by drawing the grain line ends together in two polar areas, and the spherical part is reshaped into a ring of final dimensions without breaking any of the grain lines.

PATENIEDFEH 12 19M 3,791,188

SHEET 1 BF 2 INVENTOR:

IPATENTEDIFEBIZ I574 37 1 sum 2 0F 2 INVENTORI E'WHL. DEUSSEN BY: W AGET BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to methods of dieforming metal parts and in particularto a method of die-forming metal parts in such a way that the grainlines in the final part remain uninterrupted, the part being shaped in anon-cutting cold-forming method to final dimensions without requiringany subsequent machining on a lathe, planer, or mill, and withoutrequiring any subsequent heat treatment.

2. Description of the Prior Art Normally, machine parts which receivetheir form through forging or through material-removing machiningoperations have a grain structure which is interrupted in many places.Such an interrupted grain structure can represent major problems in somecases of machine parts, the interruptions leading to hardening cracks,fatigue fractures and the like. It would be possible to avoid suchshortcomings if a solution can be found to produce these machineparts'in such a way that their grain lines remain unbroken. Of course, aprerequisite for such a condition is that the blank piece, too, has anunbroken fiber structure.

The only shape which can be produced with a substantially unbroken grainstructure is a sphere. It is known to obtain such a structure in theproduction of spheres, by inserting a cylindrical blank into the forgingdye in such a manner that the grain direction of the which it is to beshaped, and that the grain orientation of the blank is perpendicular tothe direction of compression. Using these particular dimensions for theblank and observing the perpendicular grain orientation, one obtains aspherical part which has a practically unbroken fiber structure,rendering it superior to other spherical parts. In thisforming method,the grain v line ends are virtually drawn together in a single point,

blank extends in the direction of compression. However, due to the factthat the grain lines in the end faces of the blank are broken, theforged sphere will also have broken, grain lines in one of its axes andbecause the blank is usually of a somewhat greater volume than thevolume of the fully closed forging die, the finished sphere will have asmall so-called equator" which has to be removed by grinding. Such agrinding operation, however, results in an interruption of the grainstructure, leading to situations where, under heavy shock loadconditions, the balls chip on their surface, or split into two halves.

SUMMARY OF THE INVENTION It is a primary objective of the presentinvention to suggest a method of die-forming machine parts where thegrain structure remains unbroken and where the method is easy to performand requires no additional work operations.

Inorder to attain this objective, the invention proposes a method wherethe blank is initially formed to a spherical shape with substantiallyuninterrupted grain lines, whereupon the spherical intermediate part isreshaped into the desired end shape without interrupting thesubstantially continuous grain structure. It should be understood thatthe spherical intermediate part can also be used as an end product, incases where it is desired that the end product is a sphere. The purposeof the method of the invention is in each case to obtain parts whoseimproved grain structure gives them superior resistance characteristicsover similar parts whose grain structure is broken.

In a further development of the invention, it is suggested that theblank used to produce the spherical intermediate part has the samevolume as the sphere into or at least into a very small area, so thatthe resistance of the sphere is not impaired. The spheres obtained withthis new forming method are definitely superior to those where agrinding operation is necessary to produce the final form as'in the casementioned further above.

A further suggestion of the invention provides that thespherical'intermediate part is inserted into a forging die which has arecessed forging punch and where the sphere is reshaped into a sleeve ora ring or any similar final shape. Again, the grain structure remainsunbroken after this reshaping operation, so that the sleeve or ringobtained has exceptional resistance characteristics and therefore is notsubject to prematrue aging or fatigue failure.

BRIEF DESCRIPTION OF THE DRAWINGS Further special features andadvantages of the invention will become apparent from the descriptionfollowing below, when taken together with the accompanying drawingswhich illustrate, by way of examples, several steps embodying the methodof the invention, represented in the various figures as follows:

FIG. 1 shows the forging die with a blank inserted therein;

FIG. 2 shows a spherical part as obtained by using the tool shown inFIG. 1;

FIG. 3 shows an opened forging die in which an intermediate sphericalpart is to be reshaped into a sleeve;

FIG. 4 shows a sleeve such as may be obtained by using the tool of FIG.3;

FIG. 5 shows an open ring as an alternate end product obtainable byusing the tool of FIG. 3;

FIG. 6 shows another opened forging die where an intermediate sphericalpart is to be reshaped into a ring of different cross-section; and

FIG. 7 shows the tool of FIG. 6 in its closed position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to produce the spherel of FIG. 2, a cylindrical blank 2 is inserted into the forming die ofFIG. 1 and so oriented between the die parts 4 and 5 that the grainlines 3 of the blank are oriented perpendicularly to the direction ofcompression. The volume of the blank is the same as the volume of thespace contained between the closed die parts 4 and '5. The sphere 1(FIG. 2) obtained in the first forming operation has no equator and thegrain lines 3 are drawn together into very small areas 6 and 7 atopposite poles of the sphere 1 so as to produce a body of substantiallycontinuous grain structure.

As is shown in FIG. 3, the sphere 1 can be reshaped in a forging die 8by means of a punch 9 which squeezes the intermediate sphere into thefinal shape of either a cap sleeve 10 with a closed end portion 11 (FIG.4) or a ring 12 (FIG. 5). The lines 3 in FIGS. 4 and 5 indicate thepreserved continuity of the grain structure of the final parts.

In FIGS. 6 and 7 are shown the different methods and steps for reshapingthe intermediate sphere 1 into a ring 19, by using a forging dieconsisting of two die parts 13 and 14 which carry in opposite alignmenttwo pressure spheres 15 and 16. The intermediate sphere l itself is heldin position between two brackets 17 and 18 which, as the die deforms thesphere l by closing, are retracted outside the die stroke. The sphere lis so oriented in the forging die of FIG. 6 that the two poles 6 and 7on which the grain lines 3 meet are aligned with the compression axis ofthe die. As can be seen in FIG. 7, the reshaped part has its previouspoles 6 and 7 compressed into a narrow web 20 between the pressurespheres l and 16 so that, for all practical purposes, all the grainlines inside the reshaped part 19 are continuous and unbroken. This ringis subsequently reshaped into its final form in a further forgingoperation, the latter not being a part of this invention.

It should be understood that, whenever it is desired that the sleeve orthe rings 12 have final dimensions as required by the drawing, it is anecessary prerequisite that the intermediate spherical part have exactlythe same volume as the final part. Following the forging operationdescribed above no additional machining is necessary, except forpossible surface grinding or polishing operations. Furthermore, nosubsequent heat treatment is necessary, as the required degree ofhardness is obtainable by using this constantvolume forming method.

I claim:

1. A method of die-forming parts so that, in their final shape, theyhave a substantially continuous grain structure, comprising the stepsof:

sizing a cylindrical blank with parallel, longitudinal grain lines to avolume corresponding to that of the final part desired;

inserting the blank into a forging die having two hemispherical diehalves in such a way that the direction of the grain lines isperpendicular to the direction of die closing; and

shaping the blank into a spherical part by closing the die, therebyjoining the ends of the grain lines of the blank in two narrow polarareas of the sphere. 2. A die-forming method as defined in claim 1,further comprising the steps of:

introducing the spherical part into a ring-forming die;

and reshaping the spherical part into a ring by closing the ring-formingdie in such a manner that the center portion of the sphere is displacedradially outwardly to form the ring without interrupting any grain linesin the ring. 3. A die-forming method as defined in claim 2, wherein;

the ring-forming die has a cylindrical bottom part and a cylindricalrecessed punch concentrically aligned with the latter; and the step ofreshaping involves the displacement of the sphere volume into the shapeof a cylindrical sleeve with a closed end portion across the lowersleeve face. 4. A die-forming method as defined in claim 1, furthercomprising the steps of:

introducing the sperical part into a ring-forming die which includes twopressure spheres oppositely aligned in the mating die parts, and holdingmeans for positioning the spherical part in axial alignment between theclosing pressure spheres; orienting the spherical part so that the grainjunction poles are in alignment with the movement axis of the pressurespheres; and reshaping the spherical part by closing the ringforming dieuntil the two pressure spheres are in near contact with one another andthe previously separate grain junction poles are substantially united ina narrow compressed web portion in the center of the ring. 5. Adie-forming method as defined in claim 4, wherein;

the ring-forming die has a closed volume which is equal to the volume ofthe spherical part so as to produce a ring part without a peripheralbead.

1. A method of die-forming parts so that, in their final shape, theyhave a substantially continuous grain structure, comprising the stepsof: sizing a cylindrical blank with parallel, longitudinal grain linesto a volume corresponding to that of the final part desired; insertingthe blank into a forging die having two hemispherical die halves in sucha way that the direction of the grain lines is perpendicular to thedirection of die closing; and shaping the blank into a spherical part byclosing the die, thereby joining the ends of the grain lines of theblank in two narrow polar areas of the sphere.
 2. A die-forming methodas defined in claim 1, further comprising the steps of: introducing thespherical part into a ring-forming die; and reshaping the spherical partinto a ring by closing the ring-forming die in such a manner that thecenter portion of the sphere is displaced radially outwardly to form thering without interrupting any grain lines in the ring.
 3. A die-formingmethod as defined in claim 2, wherein; the ring-forming die has acylindrical bottom part and a cylindrical recessed punch concentricallyaligned with the latter; and the step of reshaping involves thedisplacement of the sphere volume into the shape of a cylindrical sleevewith a closed end portion across the lower sleeve face.
 4. A die-formingmethod as defined in claim 1, further comprising the steps of:introducing the sperical part into a ring-forming die which includes twopressure spheres oppositely aligned in the mating die parts, and holdingmeans for positioning the spherical part in axial alignment between theclosing pressure spheres; orienting the spherical part so that the grainjunction poles are in alignment with the movement axis of the pressurespheres; and reshaping the spherical part by closing the ring-formingdie until the two pressure spheres are in near contact with one anotherand the previously separate grain junction poles are substantiallyunited in a narrow compressed web portion in the center of the ring. 5.A die-forming method as defined in claim 4, wherein; the ring-formingdie has a closed volume which is equal to the volume of the sphericalpart so as to produce a ring part without a peripheral bead.